The present invention relates to a cooling device for molds used in die casting or the like and particularly it relates to a technique for efficiently feeding fluid to a fluid flow passageway for cooling formed in a mold.
As well known, in the case of a mold used for die casting or the like, in order to form a hole in a predetermine place in a cast article, a pin section, such as a core pin, is inserted in a predetermined place in a cavity formed in the mold. It is common practice to attach a cooling device to this kind of mold for cooling said pin section.
Such cooling device comprises a fluid flow passageway formed in a pin section, a pump section for feeding cooling liquid from a liquid source to said fluid flow passageway, and a fluid feeding and discharging circuit for driving said pump section. In this case, the fluid flow passageway of said pin section is constructed such that, as shown in FIG. 9, the pin section 91 of a mold 90 is formed with a bottom-closed cooling hole 93 having spherical bottom surface 92 in the front end, positioned in said bottom-closed cooling hole 93 are the respective front end openings in concentrically disposed inner and outer pipes 94 and 95. The front end opening in the inner pipe 94 is disposed in opposed closely adjacent relationship to said bottom surface 92 than the front end opening in the outer pipe 95, in opposed relationship thereto, and a fluid flow passageway 91a is constructed so that the inner passageway 96 of the inner pipe 94 serves as a forward passageway for the cooling water while a between-pipe passageway 97 between the inner and outer pipes 94 and 95 serves a backward passageway for the cooling water. And, in performing the casting operation, the cooling liquid is fed to the fluid flow passageway 91a of the pin section 91 after the completion of the poring of molten metal into the cavity portion 98, and at the time when the molten metal has solidified and cooled to a suitable degree, the mold is opened to take out the cast article.
In this case, if the cooling liquid remains in the fluid flow passageway 91a of the pin section 91 when one lot of cast articles are produced upon the termination of the preceding casting operation, not only troubles occur in performing the subsequent casting operation but also it presents a cause of corrosion occurring in the fluid flow passageway 91a. Therefore, upon termination of casting operation for each lot is applied the so-called air purge in which air is fed under pressure to the fluid flow passageway 91a for a very short time to discharge the cooling liquid out of the fluid flow passageway 91a of the pin section 91 into the outside.
Further, this kind of pump section of the cooling device is of the so-called single-acting type in which the cooling liquid is fed only when the piston reciprocably held in the cylinder chamber moves in one way; therefore, usually the cooling liquid is intermittently fed to the fluid flow passageway 91a of the piston portion 91.
In the method of intermittently feeding the cooling liquid by using a single-acting pump as described above, however, it is difficult to feed a large amount of cooling liquid under uniform pressure continuously to the fluid flow passageway 91a of the pin section 91, so that in cooling the cast article, the quickening of application or stoppage of cooling action is hindered, leading to degradation of response. Further, such method only makes it advantageous to execute batch processing, and effecting batch processing according to this method would produce problems including one of increasing the size of the pump section or the fluid feeding and discharging circuit including the cooling liquid source, thus incurring the soaring of the cooling device costs.
Further, conventionally, to increase the pump performance, the pump section is driven by using oil pressure. Such method, however, requires not only the cooling liquid feeding and discharging circuit for feeding the cooling liquid to the pin section 91 but also an oil pressure feeding and discharging circuit including an oil pressure source for driving the pump section, and an air feeding and discharging circuit including an air source for applying air purge to the fluid flow passageway 91a of the pin section 91, thus incurring an increase in the size of the cooling device and the soaring of its costs.
Further, the temperature control of the outer surface of the pump section 91 (and the inner surface of the hole in a cast article) during molding according to the conventional method, actually, is effected depending on the cooling liquid alone which is fed to the fluid flow passageway of the pin section. And, if the termination temperature of the outer surface of this pin section 91 is too high, a release agent which is to be applied to the outer surface of the pin section 91 so as to execute the subsequent is repelled on the outer surface, making it impossible to apply a suitable amount of release agent. Further, if the termination temperature of the outer surface of this pin section 91 is too low, such release agent will flow down and fails to stick, so that in this case also it becomes impossible to apply a suitable amount of release agent.
Therefore, the termination temperature of the outer surface of the pin section 91 is very important in making high-quality cast articles; however, conventionally, since the temperature control thereof has been dependent on the feeding of the cooling liquid, as described above, it has been considered very difficult to stabilize the outer surface of the pin section 91 at a suitable termination temperature.
On the other hand, the cooling water flowing from the inner passageway 96 of the pipe 94 shown in FIG. 9 into the bottom-closed cooling hole 93 collides with the bottom surface 92 to change its direction of flow, then passing through a cooling hole inner passageway 99 existing on the outer periphery side of the inner pipe 94 into a between-pipe passageway 97 between the two pipes 94 and 96, then flowing out of the between-pipe passageway 97.
In this case, the bottom-closed cooling hole 93 formed in the pin section 91 of the conventional mold 90, as shown in the same figure, has a central region, with an axis (X) in the bottom surface 92 used as a reference, which forms a spherical surface 92x, with the outer peripheral region thereof usually forming a tapered conical surface 92y. 
However, with the central region of the bottom surface 92 thus forming the spherical surface 92x, if the cooling water from the inner pipe 94 change its direction of flow as it collides with the spherical surface 92x, the cooling water after its change of direction has produced therein a flow component which tends to converge in the vicinity of the center of the spherical surface 92x (in the vicinity of the axis (X)), said flow component flowing in the direction opposite to the flow of cooling water from the inner pipe 94 and colliding therewith. Therefore, obstruction to passage of the cooling water takes place in the vicinity of the bottom surface 92 of the bottom-closed cooling hole 93, thus causing the stagnation of cooling water. As a result, smooth outflow of cooling water is obstructed and since the lack of cooling action causes the mold 90 (core pin 91) to become heated to high temperature, there occurs an imperfection that a diecast article (for example, aluminum cast article) becomes partly fused to the mold 90.
Furthermore, the outer peripheral region of the bottom surface 92 being the tapered conical surface 92y results in a flow component which tends to converge in the vicinity of the axis (X) being produced in the cooling water which has changed its direction of flow as it collides with said conical surface 92y, said flow component flowing in the direction opposite to the flow of the cooling water from the inner pipe 94 to collide with said cooling water; therefore, the obstruction to passage of cooling water described above and the fusion of the diecast article to the mold 90 owing to said obstruction become more conspicuous.
Further, conventionally, the dimension (S) of the spacing between the bottom surface 92 of the bottom-closed cooling hole 93 and the front end of the inner pipe 94 is set usually about 10 times or more the inner diameter (d) of the inner pipe 94; more specifically, the spacing dimension (S) is usually set at 10 mm or more.
However, according to such setting, said spacing dimension (S) becomes longer than is necessary, so that the cooling water delivered from the inner pipe 94 decreases in flow rate before it collides with the bottom surface 92, so that it could flow out of the between-pipe passageway 97 as it rides on another flow of cooling water at a position short of the bottom surface 92. Therefore, this also causes an obstruction to passage of cooling water in the vicinity of the bottom surface 92, resulting in the stagnation of cooling water; therefore, smooth outflow of cooling water is obstructed in the same manner as described above, forming a main cause of fusion of the diecast article to the mold 90.
An object of the invention is to provide an arrangement wherein while reducing the size and weight of the mold cooling device, the response to the feeding and stoppage of cooling liquid is improved, thereby ensuring a satisfactory cooling action, so as to allow the termination temperature of the mold (particularly, the outer surface of the pin portion) to become efficiently stabilized at an optimum value.
Another object of the invention is to provide an arrangement wherein the shape around the bottom surface of the bottom-closed cooling hole in the mold, or the positional relationship between the bottom surface and the inner pipe is improved, thereby avoiding interference with passage of cooling liquid which occurs in the vicinity of the bottom surface of the bottom-closed cooling hole, ensuring satisfactory cooling action.
The present invention, which has been accomplished in order to achieve said objects, provides a mold cooling device having a pump section for feeding a cooling liquid to a fluid flow passageway formed in a mold, comprising an air feeding and discharging circuit which effects the driving of said pump section by air and the feeding of air to said fluid flow passageway, the arrangement being such that the cooling liquid can be continuously fed from said pump section to said fluid flow passageway. According to such arrangement, since the driving of the pump section is effected by air, the air feeding and discharging circuit for driving the pump section and the air feeding and discharging circuit for feeding air to the fluid flow passageway of the mold can be integrated, making it possible to use, for example, a single air source and a single main air passageway leading thereto. This eliminates the need for providing fluid feeding and discharging circuits of separate systems for driving the pump section and for feeding air to the mold, as in the case of driving the pump section by oil pressure, so that it becomes possible to make the fluid feeding and discharging circuit compact in size and hence to reduce the cost of the mold cooling device. Furthermore, since the pump section is capable of continuously feeding cooling liquid to the fluid flow passageway of the mold, it becomes possible to store, all the time and a little short of the fluid flow passageway (or on the upstream side), cooling liquid which is held under predetermined pressure as by a pressure adjusting valve. This eliminates the possibility of lack of cooling liquid, non-uniform liquid pressure, or the like occurring as when the cooling liquid is intermittently fed, thus ensuring a satisfactory response with which the execution or stoppage of the feeding of cooling liquid to the fluid flow passageway is effected. Further, according to such method of continuously feeding cooling liquid, there is no need for the pump section to have the power to feed a large amount of cooling liquid at one stroke; therefore, it becomes possible to achieve reduction of the size and weight of the pump section and hence to make compact in size the cooling liquid feeding and discharging circuit including the liquid source.
The concrete construction of said pump section comprises a first cylinder chamber and a second cylinder chamber which are coaxially arranged in series, a first piston and a second piston which are disposed in said first and second cylinder chambers, respectively, and a piston rod for connecting said two pistons to each other, wherein during both periods of forward and backward movements of both said pistons attending on the feeding and discharging of air to and from said first cylinder chamber, the cooling liquid is fed from said second cylinder chamber to the fluid flow passageway of said mold. With such arrangement, during not only the forward movement but also the backward movement of the piston, cooling liquid is fed to the fluid flow passageway of the mold, and since such feeding operation is continuously effected, no loss is involved in the feeding of cooling liquid. To describe in more detail, as compared with the case where cooling liquid is intermittently fed only during the forward movement of the piston, it becomes possible to feed about twice the amount of cooling liquid to the mold per reciprocation of the piston. Therefore, it becomes possible to feed a sufficient amount of cooling liquid without increasing the size of the pump section, and the cooling action is efficiently applied to the mold.
And, it is suitable to arrange that said mold be designed to form the holed convex portion of a cast article between the pin section having said fluid flow passageway formed therein and the cavity portion surrounding the outer periphery of said pin section, and that the temperature adjustment of the outer surface of said pin section and the hole inner surface of the holed convex portion contacting the same is made on the basis of (1) the feeding of cooling liquid to said fluid flow passageway and (2) the recuperative action which is consequent on the feeding of air to said fluid flow passageway immediately after stoppage of said feeding of cooling liquid. The term xe2x80x9choled convex portionxe2x80x9d refers to a convex portion formed with a hole as in a boss portion; however, this holed convex portion may be a bulging portion which is convex in the direction of the center axis of the hole or it may be an overhanging portion which is convex in a direction orthogonal to the center axis of the hole. And, the peripheral portion of the holed convex portion is formed by the cavity portion, and the hole is formed by the pin section. With such arrangement, the molten metal poured into the cavity portion during execution of the casting operation undergoes temperature drop at its surface of contact with the pin section, i.e., at the hole inner surface, owing to the cooling fluid fed to the fluid flow passageway in the pin section, and the outer surface of the pin section also undergoes temperature drop with substantially the same gradient as that for the first-mentioned temperature drop. At this stage, the outer surface temperature of the pin section is lower than that of the hole inner surface of the holed convex portion with a substantial temperature difference. And, the feeding of cooling liquid is stopped upon lapse of a predetermined time to be later described and immediately thereafter air is fed to the fluid flow passageway in the pin section. In the case where air is fed in this manner, the recuperative action of air raises the outer surface temperature of the pin section until it is substantially equal to the hole inner surface temperature of the holed convex portion, whereupon even when time elapses, both temperatures are stabilized at a substantially fixed temperature owing to said recuperative action. That is, the recuperative action of air prevents a drop in the hole inner surface temperature of the holed convex portion, and this hole inner surface temperature and the outer surface temperature of the pin section which has become substantially equal thereto settle on a substantially fixed value, whereupon even when time elapses, no difference hardly occurs between these temperatures. This makes efficient and appropriate temperature control possible about the outer surface temperature of the pin section and the hole inner surface temperature of the holed convex portion.
In this case, concerning the feeding of cooling liquid to the fluid flow passageway in said pin section, it is desirable that letting (Dx) be the outer diameter-corresponding dimension of the holed convex portion of said cast article, (D1) be the outer diameter of said pin section, (t1) be the outer peripheral thickness of said pin section, and (T1) be xe2x88x925.103+(0.621xc3x97Dx)xe2x88x92(1.068xc3x97D1)+(3.61xc3x97t1), the time (T) for feeding cooling liquid to the fluid flow passageway after completion of the pouring of molten metal into said mold be set so that the relation T1xe2x88x920.5 seconds xe2x89xa6Txe2x89xa6T1+0.5 seconds is satisfied. In addition, the time for starting the feeding of cooling liquid is suitably 0.3-0.7 second, preferably about 0.5 second after the start of the pouring of molten metal into the mold. As for the term xe2x80x9couter diameter-corresponding dimension,xe2x80x9d if the holed convex portion is cylindrical or partially cylindrical, the outer diameter of an imagined complete cylinder is the outer diameter-corresponding dimension, or if the outer shells of the axis-perpendicular section of the holed convex portion is not of true circle, such as a rectangle, polygon or ellipse, the outer diameter of an imagined cylinder having the same axis-perpendicular sectional area as that of the wall portion of the holed convex portion is the outer diameter-corresponding dimension. Judging from the above formula, it can be seen that the time (T1) serving as an index for the cooling liquid feeding time becomes longer as the outer diameter-corresponding dimension (Dx) of the holed convex portion increases, that it becomes shorter as the outer diameter (D1) of the pin section, that is, the inner diameter of the hole of the holed convex portion increases, and that it becomes longer as the outer peripheral wall thickness (t1) of the pin section increases. In the formula, the individual numerical values xe2x88x925.103, 0.621, 1.068 and 3.61 are values obtained by us conducting experiments on feeding cooling liquid and air many times with respect to many kinds of holed convex portions having (Dx) and many kinds of pin sections having (D1) and (t1), sampling cooling liquid feeding times with respect to all cases of said many kinds so as to find a high-quality holed convex portion and a temperature which is optimum for the outer surface of the pin section to have a releasing agent to be later described applied thereto, and performing predetermined calculations on the basis of such cooling liquid feeding times and respective values of (Dx), (D1) and (t1). In compliance with this formula, we have calculated the time (T1) serving as an index for cooling liquid feed, and conducted experiments on feeding cooling liquid for said time (T1) and then feeding air immediately thereafter, many times with respect to cases of many kinds different in conditions from those mentioned above. As a result, it has been found that at any rate, high-quality holed concave portions are obtained and, at the same time, that a releasing agent can be properly applied to the outer surface of the pin section. The experiments have also revealed that if the time is within the range of this time (T1), serving as an index, xc2x10.5 seconds, a holed convex portion equivalent to the above can be obtained and that the applicability for a releasing agent to the outer surface of a pin section equivalent to the above can be obtained. Therefore, although the time (T) for feeding cooling liquid to the fluid flow passageway in the pin section is optimum when T=T1, satisfying the relation T1xe2x88x920.5 seconds xe2x89xa6Txe2x89xa6T1+0.5 seconds provides good quality of cast articles and allows the casting operation to proceed smoothly without trouble.
Further, as for the feeding of air, it is preferable that air be fed to said fluid flow passageway for 5 seconds or more immediately after the stoppage of the feeding of cooling liquid to said fluid flow passageway. That is, if the feeding of air is effected for less than 5 seconds, sufficient recuperative action is not obtained, resulting in the outer surface temperature of the pin section and the hole inner surface temperature of the holed convex portion failing to assume a stabilized state in which they have a substantially fixed value, thus incurring the possibility of variations occurring between the two temperatures. Therefore, if the feeding of air is maintained for 5 seconds or more, said two temperatures can be stabilized at a substantially fixed value even if variations occur in the mold opening time after completion of the casting operation or even if the time interval from the completion of the preceding casting operation to the start of the subsequent casting operation is long. Considering that if this air feeding time becomes excessively long, it becomes impossible to stably maintain said two temperatures at a substantially fixed value, it has been decided that said air feeding time be 15 seconds or less, preferably about 10 seconds.
And, it is suitable to allow the outer surface temperature of said pin section to terminate in a temperature range of 200-250xc2x0 C. by feeding air to said fluid flow passageway. In the case where the outer surface temperature of the pin section is terminated in such range, the hole inner surface temperature of the holed convex portion also inevitably terminates in the temperature range of 200-250xc2x0 C. This allows a suitable amount of releasing agent, which consists of a viscous fluid, to be reliably applied to the outer surface of the pin section prior to the start of the subsequent casting operation after completion of the preceding casting operation. In this case, if the outer surface temperature of the pin section is less than 200xc2x0 C., then most of the releasing agent flow down from the outer surface of the pin section, with the releasing agent failing to spread well over the outer surface of the pin section, while if the outer surface temperature of the pin section is exceeds 250xc2x0 C., then most of the releasing agent is repelled from the outer surface temperature of the pin section, in which case also, the releasing agent fails to spread well over the outer surface of the pin section.
Further, it is preferable that in the passageway for discharge of air from the fluid flow passageway in said pin portion, an opening/closing valve be installed for opening/closing said discharge passageway. This makes it possible to know whether there is leakage of air from the fluid flow passageway, that is, whether there is damage, such as cracks, in the pin section, because when the casting operation is over, more specifically, after the outer surface temperature of the pin section and the hole inner surface temperature have become stabilized within the range of 200-250xc2x0 C. with air being fed to the fluid flow passageway for 5 seconds or more, the opening/closing valve closes the air discharge passageway while the feeding of air is maintained. That is, the pin section is subjected to repetition of the influence of temperature changes between high and low temperature conditions, which means that performing the casting operation many times causes damage, such as cracks; it is preferable that the pin section be replaced in early stages of generation of damage, that is, at a stage where leakage of cooling liquid from the fluid flow passageway will not cause deterioration of the quality of the cast article. Therefore, replacing the pin section on first detection of leakage of air when the casting operation is over will increase the yield of product. In addition, as for the time for closing the opening/closing valve, it may be closed each time 1 lot of casting operation is performed or preferably once every several lots of casting operation. Further, the detection of air can be made through the sense of vision or auditory sense of the human being or preferably by using a pressure detecting means (for example, a pressure gauge or a pressure switch) installed in the passageway leading to the fluid flow passageway in the pin section.
Further, preferably said fluid flow passageway is constructed in such a manner that concentrically arranged inner and outer pipes are connected to a bottom-closed cooling hole, which is formed in the mold to have a bottom surface on the front end, so that the front end opening in the inner pipe lies closer to said bottom surface than does the front end opening in the outer pipe, the inner passageway of said inner pipe serving as a forward passageway for cooling liquid, the between-pipe passageway between both said pipes serving as a backward passageway for cooling liquid, the central region of the bottom surface of said bottom-closed cooling hole being formed with a flat surface portion, whose outer peripheral region is formed with a curved surface portion which continuously extends from said flat surface portion to the inner peripheral surface of the bottom-closed cooling hole. With this arrangement, in the case where the cooling liquid delivered from the inner pipe collides with the flat surface formed in the central region of the bottom surface of the bottom-closed cooling hole to change its direction of flow, there is no possibility of a flow component being produced which tends to converge in the axial portion as in the prior art; rather, a large amount of flow component is produced which tends to diverge toward the outer periphery. Owing to this, a large amount of cooling liquid flows along the bottom surface toward the outer periphery, then smoothly changing its direction in the curved portion of the peripheral region, flowing along the inner peripheral surface of the bottom-closed cooling hole in parallel with the axis and away from the bottom surface, finally flowing out through the between-pipe passageway. And, in the bottom-closed cooling hole, since the flow of cooling liquid as described above is the mainstream, interference with passage of the cooling liquid or consequent stagnation hardly occurs in the vicinity of the bottom surface. This ensures smooth passage of cooling liquid and sufficient cooling action, thereby effectively avoiding drawbacks including the welding of the diecast article to the mold.
In this case, the diameter of said flat surface portion is set at a value preferably larger than the inner diameter of said inner pipe, and more preferably the diameter of said flat surface portion is set at about 1.5-3.0 times the inner diameter of said inner pipe. With such setting, a sufficient distance over which the cooling liquid delivered from the inner pipe flows along the bottom surface toward the outer periphery can be obtained to allow the cooling liquid to reach the curved surface portion while maintaining a suitable degree of flow rate; thus, it is possible to obtain suitable passability for the cooling liquid. In addition, if the diameter of said flat surface portion is less than 1.5 times the inner diameter of the inner pipe, it may become impossible to suitably secure the distance over which the cooling fluid flows along the bottom surface toward the outer periphery. Reversely, if it exceeds 3.0 times, there increases the amount of component which stalls and changes its direction during the time the cooling liquid reaches the curved surface portion from the flat surface portion, incurring the possibility of stagnation being generated in the vicinity of the curved surface portion.
Further, it is preferable that said curved surface portion exhibit a substantially arcuate shape in its axis-containing section. Herein, the term xe2x80x9caxis-containing sectionxe2x80x9d means a section which contains the axis, and more specifically, it means a section which is cut along the axis. With this arrangement, when the cooling liquid, which has flowed along the bottom surface toward the outer periphery, changes its direction in the curved surface portion to flow away from the bottom surface, interference with passage of flow or flow resistance increase can be minimized, so that the change of direction of the cooling liquid can be made in an optimum state.
Further, it is preferable that the spacing dimension between the bottom of said bottom-closed cooling hole and the front end of said inner pipe be set at 5 times or less the inner diameter of the inner pipe. In addition, this spacing dimension is 3 times or less, preferably twice or less the inner diameter of the inner pipe. With this arrangement, the spacing dimension between the bottom surface of the bottom-closed cooling hole and the front end of the inner pipe becomes shorter than in the prior art in relation to the inner diameter of the inner pipe, thus allowing the cooling liquid delivered from the inner pipe to reach the bottom surface of the bottom-closed cooling hole without involving lack of flow rate. This results in subsequent fresh portions of cooling liquid colliding with the bottom surface all the time, minimizing the stagnation of the cooling liquid in the vicinity of the bottom surface, ensuring sufficient cooling action, thereby effectively avoiding drawbacks including the welding of the diecast article to the mold due to lack of cooling. If the spacing dimension exceeds 5 times the inner diameter of the inner pipe, there is a danger of causing stagnation of the cooling liquid in the vicinity of the bottom surface, as in the prior art. And, setting this spacing dimension at 3 times or less, or twice or less the inner diameter of the inner pipe makes it possible to further reduce the probability of occurrence of said stagnation. In any case, said spacing dimension is preferably 1 time or more the inner diameter of the inner pipe. This is because if it is less than 1 time, the clearance between the front end opening in the inner pipe and the bottom surface is too small, decreasing the flow channel area for the cooling liquid just delivered from the inner pipe, incurring the danger of increasing the resistance to passage.
Further, the spacing dimension is set at preferably 2.0-5.0 mm, more preferably 2.5-3.0 mm. That is, if the spacing dimension is less than 2 mm (or less than 2.5 mm), the flow channel area for the cooling liquid just delivered from the inner pipe becomes small, incurring the danger of increasing the resistance to passage. On the other hand, if it exceeds 5.0 mm (or 3.0 mm), the flow rate decreases during the time taken for the cooling liquid delivered from the inner pipe to reach the bottom surface, incurring the possibility of making it difficult for the subsequent fresh portion of the cooling fluid to be fed to the vicinity of the bottom surface.
Further, it is preferable that the flow channel area of the cooling hole inner passageway formed between the inner peripheral surface of said bottom-closed cooling hole and the outer peripheral surface of said inner pipe beset at 1.5-2 times the flow channel area of said inner pipe. With this arrangement, since the flow channel area of the cooling hole inner passageway is larger than the flow channel area of the inner pipe, the resistance to the outflow of the cooling liquid (drain resistance) for the cooling liquid delivered from the inner pipe and having its flow direction changed at the bottom surface does not become too large. Furthermore, since the flow channel area of the cooling hole inner passageway is about 1.5-2 times the flow channel area of the cooling hole inner passageway, there is no possibility that the flow rate of the cooling liquid passing through the cooling hole inner passageway excessively decreases. And, if the flow channel area of the cooling hole inner passageway is less than 1.5 times the flow channel area of the inner pipe, the outflow resistance for the cooling liquid increases, interfering with the general passage of the cooling liquid and if it exceeds 2 times, the flow rate of the cooling liquid which is flowing out decreases, also interfering with the general passage of the cooling liquid.